Let's break this down. We're going to add 1066 and 1821 together.

Step 1: We'll start by adding the digits 6 & 1 in column 1 and get 7.

Step 2: We'll start by adding the digits 6 & 2 in column 2 and get 8.

Step 3: We'll start by adding the digits 0 & 8 in column 3 and get 8.

Step 4: We'll start by adding the digits 1 & 1 in column 4 and get 2.

So, 1066 + 1821 = 2887.

